1. Field of the Invention
The present invention relates to a device and to a process for treating a gas by adsorption.
2. Related Art
The present invention relates to a device and to a process for treating a gas by adsorption in an adsorber, of the type comprising the steps consisting in:                (a) compressing the gas to be treated;        (b) making the gas to be treated coming from step (a) flow through an adsorber in adsorption phase; and        (c) making a stream of regeneration fluid flow through the adsorber in the regeneration phase, and        (c1) during a first part of the adsorber regeneration phase, indirect heat exchange between, on the one hand, the gas to be treated coming from step (a) and, on the other hand, the refrigeration fluid stream is established in a heat exchanger so as to cool the gas to be treated coming from step (a) and intended for step (b) and to heat the regeneration fluid intended for step (c);        (c2) during a second part of the adsorber regeneration phase, the regeneration fluid is made to flow through the adsorber without making it undergo the heat exchange of step (c1); and        (d) auxiliary refrigeration of the gas to be treated during said step (c2) is carried out.        
A method of this type is known from U.S. Pat. No. 5,593,475.
The invention applies in particular to the separation of atmospheric air by distillation, said separation comprising an air compression step with a view to a subsequent step of cooling this air, and a step of stripping water and carbon dioxide from said air by flowing through an adsorber for the purpose of preventing the formation of ice and/or dry ice in the heat exchanger that brings the air to the cryogenic distillation temperatures.
When the gas treatment process in question is not carried out on an occasional basis but is intended, on the contrary, to be repeated or even operated continuously, the adsorber must be periodically regenerated.
For this purpose, it is known to use a regeneration gas that is made to flow through the adsorber. At least two adsorbers are then used, which switch alternately between an adsorption phase and a regeneration phase.
In the intended application, the cryogenic distillation produces a waste gas that is dry and decarbonated, and consequently capable of regenerating the adsorber.
The available mean flow rate of regeneration fluid may be limited. It may also be desirable to intentionally limit the consumption of regeneration fluid.
It is also known to improve the regenerability of the regeneration fluid by heating it, for example by electrical heating means or by steam, before making it flow through the adsorber.
However, this solution is expensive as it consumes energy.
To reduce the amount of energy consumed and/or the amount of regeneration fluid consumed, for the same result in terms of quantity and treatment quality of the heated gas, EP-A-0 456 575 proposes (FIG. 3) a process of the aforementioned type in which there is heat exchange between the compressed gas and the regeneration fluid for the adsorber.
It is an object of the invention to improve this known process in order to allow it to carry out regeneration in two successive steps, one with heated regeneration fluid, without adding a further exchanger, the other with unheated regeneration fluid.